The present disclosure generally relates to document processing devices and methods for operating such devices. More specifically, the present disclosure relates to methods and systems for adjusting the cross-process position of a drive nip in a document processing device to, for example, account for a range of media sizes.
Typical document processing devices typically include one or more sets of nips used to register and transport media (i.e., sheets) within the device. A nip provides a force to a sheet as it passes through the nip to propel it forward through the document processing device. Depending upon the size of the sheet that is being registered or transported, one or more nips in a set of nips might not contact the sheet as it is being registered or transported.
FIG. 1A depicts a top view of a portion of a document processing device known in the art. As shown in FIG. 1A, the document processing device 100 includes three sets of nips 105a-b, 110a-b, and 115a-b. The first set of nips 105a-b are used to transport a sheet; the second set of nips 110a-b are used to perform sheet registration; and the third set of nips 115a-b are used to transport a sheet in a process direction. Although two nips are shown for each set of nips, additional or fewer nips can be used. In some cases, additional nips are used to account for variations in sheet size during the transport or registration processes.
As shown in FIG. 1B, each nip in a set of nips, such as 115a-b, includes a drive roll, such as 125, and an idler roll, such as 130. A normal force is caused at each nip by loading the idler roll 130. Friction between the sheet and each nip 115a-b is used to produce a normal force that propels the sheet in a process direction. Typically, each idler roll 130 is mounted independently from the other idler rolls in a set of nips.
FIG. 2 depicts a conventional three nip embodiment for a sheet registration system. As shown in FIG. 2, the sheet registration system may include three drive modules 205, 210 and 215. Each drive module includes a drive motor, such as 205a, a drive belt, such as 205b, and a drive roll, such as 205c. The drive motor 205a is controlled by a controller (not shown) that determines the rotational velocity of a drive shaft 205d of the drive motor. Because the drive shaft 205d is operably connected to the drive roll 205c via the drive belt 205b, the drive roll can be rotated at a determined angular velocity based on the angular velocity of the drive shaft.
Each drive module 205, 210 and 215 is fixed in a known cross-process location. As such, the drive roll of an inbound drive module, such as 205c, may only contact a sheet if the sheet is of sufficient size to contact the drive rolls of all three drive modules 205, 210 and 215. As a result, drive motor 205a, drive belt 205b and drive roll 205c may be underutilized as compared with the drive motors, drive belts and drive rolls of drive modules 210 and 215.
Typical registration systems in a document processing device have fixed location drive modules for orienting a sheet prior to image transfer. The location or placement of each fixed drive module in a cross-process direction is selected in order to enable performance across a wide range of media (i.e., sheet) sizes. However, sheets that are comparatively large in size and/or weight require a wide stance for optimal control. As such, selecting fixed positions that do not account for such sizes can jeopardize hardware registration performance.